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Insecticides cause bee colonies to dwindle
Scientists and beekeepers have been observing massive bee deaths for years. Various triggers such as certain mites and parasites were already suspected. Now Scottish researchers from the University of Stirling have found that pesticides used by humans appear to play a greater role than previously thought.
Researchers at the School of Natural Sciences at the University of Stirling (UK) found that the traces of the so-called neonicotinoids (highly effective insecticides) contained in the nectar and pollen also lead to considerable impairments in the reproduction of bumblebees. The animals suffered more from malformations, the colonies affected grew significantly slower and the production of new queens was reduced by 85 percent, report Dave Goulson and colleagues in the specialist magazine "Science". In addition, French researchers had found that the pesticides applied also impair the sense of orientation of the insects, which means that they no longer find their way back to their hives.
Pesticides decide for bumble bee and bee deaths Both the results of the French researchers and the results of Dave Goulson and colleagues suggest that pesticides play a much larger role in the bumble bee and bee deaths that have been observed for years than previously thought. The two independent studies presented in the scientific journal "Science" show that the insecticides have a significant influence on the shrinkage of bees and bumble bees that can be observed. The Scottish researchers had studied the effect of the pesticides on the development of bumblebees, exposing the animals to a concentration similar to that found in pollen and nectar from crops sprayed, and then left the bumblebee in their nest for six weeks expand and then checked how much the nests with the entire content of bumblebees, wax, honey, larvae and pollen weighed.
Colonies contaminated with pesticides grow less The researchers found that the colonies in the animals contaminated with pesticides were on average eight to twelve percent smaller than in the control group. In addition, the bumblebee tended to malformation and the polluted peoples produced 85 percent fewer queens, write Dave Goulson and colleagues. The queens were crucial for the reproduction of the bumble bee in the following years, so that the insecticides also show a delayed effect here, which only becomes noticeable one year after the actual pesticide exposure. The number of queens is directly related to the number of new nests in the coming winter, the Scottish scientists report. According to Dave Goulson, insecticides have a massive impact on the observed decline in bumble bee populations worldwide. "Some species of bumblebee have declined enormously," emphasized the expert, citing North America as an example, where "some species have more or less completely disappeared from the continent". According to Goulson, three species have already been wiped out in Great Britain. "Given the extent of the use of the neonicotinoids", it can be assumed that the pesticides have a significant share in the mass extinction of bumblebees and bees, according to the Scottish researchers.
Pesticides influence the sense of orientation of bees The study by the French researcher led by Mickael Henry from the Institut National de la Recherche Agronomique in Avignon also suggests that the pesticides have a more serious impact on bee and bumblebee populations than previously thought. As part of their study, Henry and colleagues attached tiny microchips to the bodies of bees that they could use to track the animals' flight rod. After some of the experimental bees came into contact with the insecticide thiamethoxam, their sense of orientation seemed to be significantly impaired, write the French researchers. The animals concerned had died two to three times more frequently than their bees, which was not in contact with the insecticide, according to Henry and colleagues. The flight routes determined using the data from the microchips showed that the polluted bees eventually reached a distance from their nest, which made it much more difficult for them to return. According to the French researchers, the toxins sprayed by humans could help prevent a growing proportion of the bee from finding its way back to its hive.
Food crisis due to bee death? The decline in bee and bumblebee populations has led to intense discussions in recent years about the possible causes and consequences of bee and bumblebee deaths. Because the useful insects play a crucial role in the ecosystem. They pollinate billions of plants and ensure that they bear fruit or can reproduce. If the bees are missing, this could trigger a global food crisis, according to the United Nations (UN). The performance of insects is also of considerable importance as an economic factor, since large parts of agriculture would not function without their contribution. In the long term, if the bees are missing, the plant-based food base could continue to shrink, which would massively decrease the availability of food. An adequate supply of the population would not be guaranteed without the support of the useful insects.
Long-term loss of yield due to the use of pesticides The search for the causes of the global bee death is therefore in full swing, whereby besides the insecticides or pesticides, above all the aggressive varroa mites are suspected as triggers. The mites bite the bees and can result in the death of the animals. The mites can reproduce easily in the sticks, which may result in the loss of entire colonies. Since the mites stay active longer and can spread better at the relatively mild temperatures, the weather also plays a role in the increased bee mortality, according to the experts. Furthermore, special parasite flies are suspected of promoting the death of the bees. However, the current study results suggest that the pesticides used by humans have a far greater share in bee death than previously thought. A rethink should take place as soon as possible out of simple interest of the individual. Because the short-term increases in yield that can be achieved with the help of pesticides can quickly lead to a considerable drop in yield if the bee population continues to decline. (fp)
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